INDIVIDUAL CONTROL BY INDIVIDUAL VAV - APACS from Argon Air

INDIVIDUAL CONTROL BY INDIVIDUAL VAV
Hans F. Levy, P.E., Life member of ASHRAE
President, Argon Corporation
www.argonair.com
4968 Tamiami Trail North
Naples, FL 34103
information@argonair.com
239.430.7876
239.430.7877 Fax
INTRODUCTION
Individual control is needed and can be cost
effective. “Thermal Comfort,”Chapter 8 in the
ASHRAE Handbook of Fundamentals, 2001,
indicates vast differences between people’s
needs for thermal comfort, strongly indicating
the need for individual control. Metabolic heat
generation varies in a ratio as high as ten to
one (Table 4, Chapter 8, ASHRAE Handbook
of Fundamentals, 2001.) The system
described below was installed in a bank in 20
work areas. In a two year period there was not
a single complaint. Occupants and
management enjoyed 100% satisfaction.
Fanger et al. (1973, 1985, 1986 and 1989)
demonstrate in many studies that personal
comfort will lead to greater employee
productivity, greater satisfaction and lower
turnover. Note that typical employee costs
today are $3000/sm/yr ($300/sf/yr), versus
$300/sm/yr ($30/sf/yr) for other building costs.
Therefore the results of individual control are
great savings in personnel costs, the greatest
cost of an office building operation.
DISCUSSION
Since maintaining different temperatures in
close quarters is impractical, varying air
velocity (VAV) through personal air outlets,
adjustable by occupants, is the best method of
providing personal control. This requires
redesign of office buildings. Accomplishing
delivery of personal air flow to every
workstation is also impractical, except by
means of raised access floor, which is now
widely and increasingly used in office
buildings.
The effectiveness of this approach was tested
and proven at the University of California at
Berkeley by Fred Bauman, et al., and
published as “Lab Test of APACS,”24 April
2000. The tests show that by varying the
airflow, occupants can effect a change to
achieve individual thermal comfort.
TEST CONDITIONS
Tests were designed to compare heat removal
by moving air compared to changes in ambient
temperature. The tests covered two room
temperature setpoints (26 and 28°C [79 and
82°F]) and both horizontal and vertical
mounting positions of the Argon Personal Air
Conditioning System (APACS). For each room
temperature a reference test was first
performed in which the mannequin was tested
with no air flow from the APACS unit. Cooling
tests were performed at different air volumes
and temperatures at both the 26°C (79°F) and
28°C (82°F) room temperatures. The majority
of tests were done at the 26°C (79°F) room
temperature with horizontal position of the
APACS, for which the supply temperatures
studied were 21°C, 23°C, and 25°C (70°F,
73°F, and 77°F). At 28°C (82°F) room
temperature with horizontal position and 26°C
(79°F) room temperature with vertical position,
only the 21°C (70°F) supply temperature was
studied. Four air supply volumes were tested
to cover the range of supply rates expected
from the APACS unit. The volumes tested
were 10, 30, 50 and 70 cfm (5, 14, 24, and 33
L/s). All volumes were tested at the 26°C
(79°F) room temperature setpoint with
horizontal position, while only the 30 and 70
cfm (14 and 33 L/s) rates were tested for the
28°C (82°F)/horizontal and 26°C
(79°F)/vertical tests. The APACS unit was
tested under focused air flow direction,
meaning the air supply was directed toward
the mannequin in a way that maximized the
overall (whole-body) cooling rate. Tests were
designed to measure worst case conditions.
The study only tested for sensible cooling. As
reported in the test document, prior tests with a
wet mannequin indicate that the cooling effect
would be at least doubled (“Lab Test of
APACS,”p. 11). The result is that, if the
occupant can vary airflow, he can increase or
decrease the heat removal over a wide range,
with the same results as changing the

temperature of the air. The study shows that
the cooling effect range is up to 8°C or 14°F. In
other words, with a room temperature of 28°C
(82°F) an occupant can change his
environment from the ambient temperature to
20°C (68°F) with full airflow, and he can do this
without affecting his neighbor. This range
offers enough variety to make everyone
comfortable and happy under almost any
circumstance. As the test data clearly show, it
is not necessary to change the ambient
temperature to provide personal comfort. The
tests also show that it is practical to ramp the
temperature up to utilize stored cooling in the
building and to reduce peak demand as well as
required equipment capacity.
Figure 1
Air speed required to offset increased
temperature. The air speed increases in the
amount necessary to maintain the same total
heat transfer from the skin. This figure applies
to increase in temperature above those
allowed in the summer comfort zone with both
t r and t a increasing equally. The starting point
of the curves at 0.2 m/s (40 fpm) corresponds
to the recommended air speed limit for the
summer comfort zone at 26°C (79°F) and
typical ventilation (i.e., turbulence intensity
between 30% and 60%). Acceptance of the
increased air speed requires occupant control
of the local speed. [ANSI/ASHRAE 55-1992,
p. 9, Fig. 3]
DESIGN
The concept of using air movement for control
instead of temperature change is not new. It
has been used in airplanes and automobiles
for many years. However, the limited space in
vehicles, and the need to move sufficient air to
effect the necessary cooling, results in too high
a velocity, which feels drafty. In general there
is not sufficient space to limit the velocity to an
average of less than 1 m/s (200fpm). This is
approximately two miles per hour and meets
ANSI/ASHRAE 55-1992 (see Fig. 1). In offices
there is usually more than enough space to
move sufficient air while adhering to the above
limits.
In order to limit the air velocity as described
above, to provide air to the occupants below
room temperature, and not to lose the
effectiveness of the moving air, the air must be
discharged very near the person. The ideal
distance is in the vicinity of 30 centimeters
(one foot) or less. This proximity also provides
the individual occupant with immediate
response to changing environmental
conditions or personal comfort preference.
Being close to the occupant also increases
ventilation efficiency. ANSI/ASHRAE Standard
62-1999, “Ventilation for Acceptable Indoor Air
Quality,”(Second Public Review, August
2001), p. 6, suggests a zone air distribution
effectiveness greater than 1.0 for low velocity
displacement ventilation. This means a
substantial reduction in required outside air
and a very substantial energy saving. This
arrangement permits the use of a simple
manual damper control within easy reach of
the occupant.
Figure 2
Desk air terminal (vertical)
Giving everyone personal control with a
personal air outlet leads to a question: what to
do with common space. A simple solution is to
combine the personal outlet with a room outlet
that keeps direct room air away from the
occupant. The introduction of room air needs
to be far enough from the occupant so that it
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does not interfere with the personal control.
The combined airflow is designed to meet the
cooling load of the person, the workstation and
the adjacent area. If properly designed, the
occupant can turn off the personal air supply
without materially affecting total airflow. With
this arrangement total airflow is relatively
constant. Overall room temperature is then
controlled from a space thermostat which can
control the capacity of the air handler to meet
the load requirements (see Figs. 2, 3 and 4).
energy consumption stems from the higher
operating room temperatures and the reduced
fresh air requirement.
Figure 4
Floor/desk air terminal (horizontal)
Figure 3
Partition air terminal
The room outlet can be a floor grille outside
the workstation, or a separate grille mounted
either in the furniture or in a space partition
pointing to open space. This outlet may also
exhaust through the top of furniture partitions
(as was done at the bank installation
mentioned above). The latter arrangements
eliminate floor grilles and leave the floor clear
for furniture placement and easier
housekeeping.
Fan air terminals are used in the access floor
plenum 1) to produce the necessary static
pressure for personal and room air outlets, 2)
to eliminate air leakage out of the building
(buildings are not airtight), and 3) to reduce
distribution ductwork. They must be efficient,
with low noise levels and a trouble free, long
life. The additional energy use by these fans is
offset by reduced energy consumption in the
main air handler. The system reduces overall
energy consumption by eliminating air leakage
and reducing total fan horsepower because of
greatly reduced ductwork. Additional reduced
This arrangement also makes balancing the
system much simpler. Fans can be added for
additions in load at any time. For relocation
and remodeling of workstations the fans can
be easily moved, since there is no need to
fasten them in place. They are simply located
on the sub floor where needed.
ANSI/ASHAE 55-1992, Para 5.1.6.3, stipulates
a minimum underfloor temperature of 18°C
(65°F). When supplying air at this temperature
through a cooling coil, it is difficult to properly
control humidity and impossible to use ice
storage. The best strategy is to design the air
handler cooling section to suit the chilled water
or dx system and to bypass sufficient return air
to get the leaving air temperature up to the
desired temperature. This approach can use
face and bypass dampers to control humidity
and eliminates all saturated air from the space.
Also, elimination of mixing in the occupied
space produces a cleaner environment.
Particles lighter that air will float up to high air
returns and the system filters, instead of being
recirculated by secondary air movement.
CONCLUSION
The system described above will air condition
individual people instead of the building. It
thus will eliminate dissatisfaction with thermal
conditions (the number one complaint in most
offices), lead to greater productivity and reduce
the greatest cost in any office building, the
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payroll. By offering sustainability, reduced
energy cost and a cleaner environment, it is
the basis for a more efficient, more productive
“green building.”
ACKNOWLEDGEMENTS
Special thanks for the development of the
system go to Hank Spoormaker, PE, now
deceased, who conceived of the zero pressure
plenum twenty years ago in Johannesburg,
South Africa. Appreciation also goes to Fred
Bauman, UC Berkeley, whose support and
diligent testing helped crystallize a lot of the
concepts, and last, but not least, to Peter Betz
and many others whose belief in a better
system helped me to carry the ball.
CODES AND STANDARDS
ASHRAE. 1989. Ventilation for Acceptable
Indoor Air Quality. ANSI/ASHRAE
Standard 62-1989.
ASHRAE. 1992. Thermal Environmental
Conditions for Human Occupancy.
ANSI/ASHRAE Standard 55-1992.
ASHRAE. 2001. ASHRAE Handbook of
Fundamentals 2001.
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